Recent studies have indicated that there is a quantum relationship between amount of preoptic area (POA), electrochemically stimulated and the quantity of luteinizing hormone released into plasma. In the next year we shall attempt to relate such discharge to alterations in median eminence concentrations of tyrosine hydroxylase, and the biogenic amines. Chemical measurements of such amines will be performed before and after POA stimulation. In other studies, the importance of the preovulatory release of estrogen and of circadian rhythms of adrenal progesterone secretion will be evaluated in terms of time and concentration of preovulatory LH release and alterations in thresholds of excitability within the hypothalamus. Further studies also will evaluate the effects of the sex steroids on pituitary responsiveness to LRF in a newly devised superfusion system. Cyclic AMP, LH and prolactin will be measured as endpoints. Other studies of this type involve time of appearance and localization of LRF in developing and adult human hypothalamus employing the same superfusion system. Finally, the effects of biogenic or indole amines on LRF secretion following ionoelectrophoresis into the median eminence or arcuate nuclei will be evaluated.